Various olefins are known to react at elevated temperatures with carbonyl compounds, e.g. carboxylic acids, in the presence of manganic compounds to produce various carbonyl compounds; for example, .gamma.-vinyl-.gamma.-butyrolactone is produced at 140.degree.-180.degree. C. by the reaction of butadiene and acetic acid. .gamma.-vinyl-.gamma.-butyrolactone is known to be converted to sorbic acid by heating in the presence of particular acid catalysts.
Sorbic acid is a useful article of commerce, being particularly useful in food preservation applications. Sorbic acid is presently produced commercially by a process involving reaction of ketene and crotonaldehyde.